Studies are to be conducted on the cardiovascular and related effects of certain Cl9 steroids. The same is to be done with other known or potentially active mineralocorticoids of the C19 series, such as 18-hydroxy deoxycorticosterone and l6, l8 dihydroxy deoxycorticosterone. In addition further studies on the cardiovascular effects of sodium chloride as such will be pursued. Recently mineralocorticoid receptors have been identified in the wall of the aorta. The possible significance of vascular mineralocorticoid receptors in the genesis and progress of certain forms of naturally occurring and induced hypertensive disease will be examined. Whether or not the number and specific affinity of these can be modified experimentally, and whether these parameters can be related to sensitivity or resistance to hypertension will be the subject of investigations to be conducted.